Numerical simulations of the effect of turbulence intensity and integral length scale on stagnation region heat transfer

Abstract

Numerical simulations of stagnation region heat transfer for laminar and turbulent freestreams have been performed using a commercial CFD code CFX-TASCflow. Prior to the stagnation region simulations, some classical flow problems were solved to validate the CFD code and evaluate the different turbulence models. Simulations were performed for flow in a square driven cavity, laminar and turbulent boundary layers on a flat plate and flow over a backward facing step. The simulation results are in good agreement with previous simulation results, experiment and theory. The simulations of stagnation region heat transfer with a laminar freestream are performed at Reynolds numbers ranging from 6.5x10³ to 6.5x10⁵. The laminar freestream simulations were performed to obtain an appropriate grid structure and simulation parameters. The laminar simulation results are in good agreement with results of Rigby and VanFossen. The simulations for a turbulent freestream are performed at Reynolds numbers of 1.3x10⁴, 5x10⁴ and 1x10⁵, turbulence intensities of 1%, 3% and 5% and the ratio of integral length scales to leading edge diameter (ʎ/D) of 0.4282, 0.5709 and 0.7136. The k-ε turbulence model proposed by Kato-Launder is used for the simulation. The heat transfer results from the simulations are compared with the empirical solution of VanFossen, et al. The heat transfer increases with Reynolds number and turbulence intensity, and decreases with integral length scale.